236 Evolution and Adaptation 
the gemmules that have collected in it. The fifth assumption 
is that the gemmules are thrown off at all stages of develop- 
ment; the sixth, that in their dormant state they have a 
mutual affinity for each other; the seventh, that there may be 
a sort of continual competition in the germ-cells between the 
original gemmules and the new ones, and, according to which 
win, the old or the new form develops. Thus we see on 
closer analysis that the pangenesis hypothesis is made up of 
a goodly number of different assumptions. At least half a 
dozen imaginary properties are ascribed to the imaginary 
gemmules, and these attributes are all essential to the 
working of the hypothesis. 
Some of the more obvious objections to the hypothesis 
have been stated by Darwin himself. Such, for instance, as 
our ignorance at what stage in their history the body-cells are 
capable of throwing off gemmules, and whether they collect 
only at certain times in the reproductive organs, as the 
increased flow of blood to these organs at certain seasons 
might seem to indicate. Nor have we any evidence that they 
are carried by the blood atall. The experiment of Galton, of 
transfusing the blood of one animal into another, and finding 
that this produced no effect on the young that were born 
later, might be interpreted to mean that gemmules are not trans- 
ported by the blood; but this kind of experiment is inconclu- 
sive, especially in the light of recent results on the effect of 
the blood of one animal on that of another. 
A part of the evidence on which Darwin relied to support 
his theory has been shown to be incorrect by later work. 
Thus the assumption that more than a single pollen grain, or 
more than one spermatozoon, is necessary in some cases for 
fertilization, is certainly wrong. In most cases, in fact, the 
entrance of more than one spermatozoon into the egg is dis- 
astrous to the development. The cases referred to by Dar- 
win can probably be explained by the difficulty that some of 
the pollen grains, or spermatozoa, may have in penetrating 
